You will get an empty screen with a warning that modifying these
files can lead to system problems. You are given an option to show
the files by clicking on "show files". Do that to display the
contents of the folder.

Double click on the folder "System"

You will get another message like in step 3. Click on "show files"

Look for a file called "conagent" and select it by clicking once
(you will probably have two, one with the MS-DOS icon, the other
with a blue window icon, they are really the same so you can use
either one).

Right-click (using the right button on your mouse) on "conagent"
and select the "Properties" option.

Click on the "Screen" tab.

In the first part of the panel, on the right-hand side, select the
size to be 50 lines.

In the middle section of the panel, unselect "Restore settings on
startup".

Close the window. From now on, every time you run a program from
within Visual C++, you will get a window with 50 lines.